Human herpesvirus 8 (HHV-8), also called Kaposi's sarcoma- associated virus (KSHV), was first identified in 1994 in AIDS Kaposi's sarcoma biopsies. Kaposi's sarcoma (KS) was a relatively rare angiogenic neoplasm that dramatically increased in incidence with the onset of the AIDS epidemic. Approximately 20 percent of gay and bisexual men with AIDS develop KS. HHV-8 is also consistently assoicated with two other malignancies in AIDS patients: Multicentric Castleman's disease and a subset of non-Hodgkin's lymphomas called primary effusion lymphomas (PELs) or body cavity based lymphomas (BCBLs). PELs have the unusual feature that the majority are co-infected with both HHV-8 and another human gamma herpesvirus Epstein-Barr virus (EBV). HHV-8 and EBV each encode multiple growth stimulatory genes and the potential exists for inter-virus interactions that modulate the program of HHV-8 or EBV gene expression to allow the development of this particular malignancy. A goal of this research project is to better understand the consequences of dual infection in PELs. LANA is one of the few HHV-8 genes that is expressed in latent infection and in all HHV-8 associated tumor cells. LANA's role in the maintenance of HHV-8 latency and in PEL cell development will be explored. The Specific Aims of this proposal are: Aim 1. EBV latency gene expression, promoter usage, genome copy number and status (episomal or integrated) will be examined in PEL cell lines. The possibility that HHV-8 LANA can modulate EBV latency promoter activity will be examined. Aim 2. A genetic assay for the contribution of HHV-8 latency genes to PEL development will be established. Aim 3. The HHV-8 latency protein LANA will be characterized to determine its contribution to HHV-8 latency DNA replication and its potential contribution to tumorigenesis through modulation of cellular gene expression.